The invention concerns a cervical vertebra plate for osteosynthesis, having at least two receiving openings for the screw heads of bone screws to secure the cervical vertebra plate to two cervical vertebrae, wherein the receiving openings have a fluting, in particular a longitudinal fluting, in the distal region about the periphery thereof. The invention also concerns a bone screw, in particular, for a cervical vertebra plate of this type, comprising a screw head and a threaded screw shank, wherein the outer periphery of the screw head has a fluting, in particular, a longitudinal fluting.
Bone plates are known per se, e.g. from DE 199 50 270 A1. Bone plates of this type are e.g. secured to vertebrae to orient and stabilize them. Towards this end, the individual bone plates are connected via rods, wherein the rods are mounted, in particular clamped, to the bone plates.
Bone screws are used to secure the bone plates to vertebrae. The screws penetrate through the bone plates and are screwed into the vertebra. The bone plate is usually held via the screw head.
U.S. Pat. No. 5,275,601 also discloses a bone screw which is supported with its fluted conical screw head in a receiving opening of a plate. The plate is secured to the bone via these screws.
It is the underlying purpose of both of these bone plates to optimally adopt the forces acting on the bone such that they are either transferred to a neighboring bone or bone part or to correction or fixation rods. Towards this end, the screw head must in any case be optimally supported in the receiving opening of the bone plate to prevent play between the screw head and receiving opening. Securing to prevent inadvertent unscrewing is effected by the fluting provided on the inner periphery of the receiving opening and/or the outer periphery of the screw head.
It is the underlying purpose of the present invention to introduce a system which provides a safer, tight connection, i.e. optimum support of the outer peripheral surface of the screw head on the inner peripheral surface of the receiving opening of the bone plate.
This object is achieved in accordance with the invention with a cervical vertebra plate of the above-mentioned type in that the depth of the fluting increases from a proximal to a distal end.